Add GitHub action for project build

.github/workflows/gradle.yml

@@ -0,0 +1,26 @@
+name: Project Build
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v1
+
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+
+      - uses: actions/cache@v1
+        with:
+          path: ~/.gradle/caches
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Build with Gradle
+        run: ./gradlew build